1. Technical Field
The present invention relates generally to paving material, and more particularly, to a pavement ramp edge maker, paving machine and related method.
2. Related Art
Typically, screed pavers include a self-propelled paving machine having a hopper for receiving paving material, e.g., asphalt, from a truck so that the truck progressively dumps its load of paving material into the hopper. A conveyor system on the paving machine transfers paving material from the hopper rearwardly for discharge onto the roadbed in front of transversely arranged screw augers, which spread the material laterally in front of a main screed. This main screed functions to compress and level the paving material distributed by the augers to give a smooth finished road surface. The height and attack angle of the main screed may be varied to control the depth and surface of the pavement mat. The main screed may also include screed extenders to allow for a wider pavement mat to be laid. Subsequently, the paving material is compacted in position by, for example, a rolling machine or tamping machine.
A safety problem generated by basic paving machines are drop off edges that are left at a side or an end of a mat of paving material. Drop off edges are a safety problem because vehicles may catch a side of a tire on them, causing the vehicle to lose control. Drop off edges may range in size from a half inch to more than 2 inches, and may exist prior to and after compaction. Drop off edges can be found in highways, secondary roadways, parking areas, driveways, drainage sections, and a variety of other locations. The inherent safety issues generated by drop off edges have been identified in a report by the American Automobile Association's (AAA) Foundation for Traffic Safety that was prepared by the Transportation Center at the University of Tennessee entitled, “The Elimination or Mitigation of Hazards Associated with Pavement Edge Dropoffs During Roadway Resurfacing.” In addition, evidence of the road edge drop-off safety problems is provided by the large number of lawsuits filed against cities, counties and states as reported in the Road Injury Prevention & Litigation Journal.
Drop off edges may be generated during paving at, among other areas, two notable situations. First, drop off edges are frequently generated when paving multiple active traffic lanes, where it is oftentimes impossible to pave two or more lanes in a short time span. The inability to pave two or more lanes quickly may be due to a variety of reasons, e.g., traffic, equipment shortages, etc. In this case, a drop off edge is oftentimes left between a first active traffic lane over which a new pavement mat has been laid and a second active traffic lane upon which new pavement has yet to be laid. One approach for solving this type drop off edge is disclosed in U.S. Pat. Nos. 6,238,134, 6,238,136, 6,270,284 and 6,283,672. In each of these devices, a pavement edger is fixedly mounted to a main screed or screed extension of the paving machine, and moves as an integral unit with the main screed. The pavement edger generates a stepped tapered ramp having a highly compacted step and a highly compacted upper portion of the tapered ramp. The ramp eases a vehicle's transition over the drop off edge and solves a number of paving problems relative to laying the next lane's mat.
Second, referring to FIG. 1, a drop-off edge 10 may be generated between a newly repaved area 12 and an adjacent non-repaved area 14. Non-repaved area 14 may be, for example, an emergency lane surface 18 of a main highway, a shoulder 18 of a secondary road, an unpaved area 18, etc. In any event, the side of pavement terminates as a drop off edge 10 having an inclination λ greater than 45°, which is generally considered an unsafe inclination. This type drop off edge oftentimes poses a significant safety problem because of obstacles such as trees, guard rails, etc., that may exist proximate the non-repaved area 14.
In a worst-case scenario, this type drop off edge 10 is not corrected and the current non-repaved area 14 is left as is. One approach to diminish this type drop off edge, however, has been to spread gravel 20 from a top edge 22 of the new pavement mat 16 to the non-repaved area surface 18. Unfortunately, this approach does not provide a permanent solution since the gravel eventually loosens and is thrown off the road. Further, this approach is fairly expensive since it requires additional passes over the area.
Ideally, a remedy for roadside drop off edge 10 should be provided during paving because each re-visitation to a site costs time and money. One approach used during paving has been to provide a strike off on an end of the paving machine screed to form a ramp. A strike off is a vertical plate attached to the screed or an opening in the screed that scrapes a ramp into the paving material passing thereunder. Unfortunately, a strike off does not adequately solve this type drop off edge because it provides hardly any compaction, which permits the ramp to be readily torn apart. In addition, a strike off tends to tear the edge of the mat causing a non-straight and disfigured pavement edge. Tearing of the edge of the mat also reduces the integrity of the mat, which decreases the life of the pavement.
The pavement edger described in the above-identified patents is impracticable relative to a drop off edge 10 adjacent a non-repaved area 14 for a number of reasons. First, the pavement edger is coupled to a main screed or screed extension of a paving machine. As a result, the pavement edger is incapable of following undulations that are common in non-repaved traffic areas. Second, the ramp generated includes vertical edges for mating with subsequent pavement mats. This ramp, although significantly better than an inclined drop off edge 10, is not designed to be a permanent remedy to drop off edge 10.
In view of the foregoing, there is a need in the art for a pavement edge maker that addresses the problems with the related art.